Ika Musume hatched in the ocean near Japan, residing there before deciding to invade the surface world as retribution for human pollution of marine environments. Her initial plan involved using the Lemon Beach House restaurant as an invasion base, disrupted when she accidentally damaged the establishment's wall while attempting to swat a mosquito. Consequently, she worked there as a waitress to repay the repair costs, leading her to reside with the Aizawa siblings who operated the restaurant. Physically resembling a young human girl, Ika Musume possesses distinctive cephalopod features: ten blue, prehensile tentacles extend from her head, functioning as both hair and versatile limbs capable of lifting heavy objects, regenerating if severed, and exhibiting exceptional dexterity for activities like sports or art. A white, mantle-shaped structure atop her head—often mistaken for a hat—is integral to her biology and cannot be removed without fatal consequences; its fins move like those of a squid. She typically wears a self-repairing, stain-resistant white dress with light blue accents, thick blue bracelets enabling instantaneous weight adjustment (from 0.0005kg to 20,000kg), and white ankle boots. Her abilities include spewing high-quality squid ink used in cooking, bioluminescence for nighttime illumination, underwater breathing via gills, and environmental adaptations like rapid drying and tan-resistant skin. Her personality blends determination with naivety. Initially focused on world domination, she is easily distracted by human experiences like television, video games, or culinary delights—particularly shrimp, which she craves obsessively. She exhibits childlike curiosity and impulsiveness, leading to comedic mishaps. Deep-seated fears include natural predators like sharks and killer whales (even inflatable versions), fire due to its lethality to marine life, and specific individuals: Chizuru Aizawa’s intimidating strength, Sanae Nagatsuki’s obsessive advances, and Cindy Campbell’s attempts to prove her extraterrestrial origins. She ends sentences with "de geso" (でゲソ), reflecting her squid identity. Character development unfolds across her surface experiences. Early episodes depict her underestimating humanity and struggling with surface-world norms, but gradual bonds with humans soften her antagonistic goals. Key relationships include: - Eiko Aizawa: Initially a strict taskmaster, their dynamic evolves into mutual care, exemplified when Ika regrows tentacles to save Eiko from drowning. - Chizuru Aizawa: Feared yet respected; Chizuru’s maternal role culminates in accepting Ika’s deliberate vandalism to extend her stay at Lemon. - Takeru Aizawa: Views her as an older sister figure, engaging in playful activities. - Nagisa Saitō: Valued for genuine fear of Ika’s invasion threats, contrasting others’ indifference. Temporary loss of her squid abilities due to prolonged air exposure forces identity reevaluation, though emotional crises—like saving a life or confronting predators—restore them. In later manga arcs, after repaying her debt, she deliberately damages Lemon again to remain with the Aizawas, symbolizing her shift from invader to family member. OVAs highlight her integration, such as participating in a message-in-a-bottle initiative or assisting Ayumi Tokita’s puppy, Rentarō. Her journey consistently emphasizes adaptation and belonging over conquest.